FIELD OF THE INVENTION
The invention relates to a delivery system of a sheet-processing machine, more particularly, a printing press, for transporting a respective sheet in a conveying direction along a sheet-conveying path to a stacking device, the delivery having a sheet braking device engaging, during operation, with an underside of a respective sheet and retarding it by means of suction belts or the like; a suction region disposed adjacent to and upstream of the sheet braking device, as viewed in the sheet-conveying direction; a suction device for applying suction, in the suction region, to the underside of the respective sheet; a brake carriage carrying the sheet braking device and the suction device and being displaceable between selective positions within a segment of the sheet-conveying path; a stationary first guide device formed with a first sheet guide surface segment set back upstream from the sheet braking device, as viewed in the sheet-conveying direction; and a second guide device having a guide element displaceable by means of the brake carriage and forming a second sheet guide surface segment located between the sheet braking device and the first sheet guide surface segment, the second sheet guide surface segment, together with the first sheet guide surface segment, forming a combined sheet guide surface having a telescopically variable length.
A delivery system of the foregoing general type has become known heretofore from the published German Patent Document DE 25 44 566 A1 and is provided for non-smearing guidance of sheets printed in a first form and perfector printing process, i.e., on both sides thereof, by a sheet-fed printing press along a sheet-conveying path between a final printing unit of the sheet-fed printing press and a sheet braking device. In a consequent application of the basic principle of forming the sheet guide surface as free of gaps as possible, only one relatively narrow gap, which is limited or defined by a guide plate on the sides of the suction wheels provided to slow down the sheets, is provided between the suction wheels and an end of a sheet guide plate which faces towards them and is adjustable together therewith. During operation, negative pressure produced in accordance with the so-called injector principle prevails in this gap and applies suction to the underside of the respective sheet. In response to this suction, the trailing edge of a slowed-down leading sheet, in particular, is intended to dip out of the way downwardly in order to avert any collision with the leading edge of a yet unbraked trailing sheet. The faster the sheets follow one another, the more difficult it is for this downward out-of-the-way dip or movement to be achieved.